The true tale of pioneering 18th century barrister William Garrow, who acted as counsel for the accused, introducing the concept of 'innocent until proved guilty' at London's Old Bailey.
William ends up risking his reputation as he returns to the Bailey to defend James Hadfield, who is on trial for high treason for trying to eliminate King George III. He continues to enjoy an "irregular" relationship with Lady Sarah Hill and finds himself ostracised and impoverished. Separated from her husband, Sarah learns from Southouse that she has no independent rights of her own.
Garrow is looking for a challenge, so he agrees to defend two Spitalfield weavers accused of destroying silk looms in an act of industrial espionage - a tough case that becomes more difficult when one defendant testifies against his friend, leaving the barrister conflicted. Meanwhile, Southouse is furious with Lady Sarah for trying to get custody of Samuel.
General Thomas Picton, the Governor of Trinidad, is accused of allowing the torture of a young mixed-race girl - and in prosecuting, Garrow is keen to expose the injustice of the colonial system. But he faces a dilemma when Melville offers him a proposition - if he will limit his prosecution, the lord will use his considerable influence to reunite Lady Sarah with her son.
Garrow successfully defends a man falsely accused of murder at a polling day riot. Approached by the victim's daughter Garrow agrees to find and prosecute the real murderer putting himself in grave danger from the man's colleagues and chief magistrate of the constabulary. Lady Sarah seeks documents to discredit Lord Melville and legally regain her son.